This invention relates to sealing rings for adjacent flange surfaces, especially seal rings utilizing plastic deformation.
Mechanically separable joints in ultra high vacuum systems are most reliably sealed by plastic deformation of metal elements or gaskets. Typical seals are:
(1) Crushed wire rings, of gold, copper, or aluminum PA1 (2) Step seal with flat gasket PA1 (3) Coined gasket seal PA1 (4) Knife edge seal PA1 (5) "Conflat" seal (Varian Associates) PA1 (6) "Cryofit" tube fitting (Raychem Corporation) PA1 (7) "Helicoflex" seal (Carbone-Lorraine Industries Corporation)
In all these seals the sealing force is applied normal to the seal line, because no relative motion of the seal elements can be tolerated other than plastic deformation.
Some very large vacuum systems potentially of great importance cannot be sealed with any of these closure systems because the components to be sealed together cannot approach each other along paths perpendicular to the mating surfaces. An example of such seals are those between torus sections of a 16-segment vacuum vessel of a segmented Tokamak Fusion reactor. Each wedge-shaped segment spans 221/2.degree. and the closure surfaces approach each other along a sloping path of 111/4.degree., i.e., 783/4.degree. away from the normal. During gasket compression therefore the sliding between seal surfaces would be roughly five times as great as the gasket compression. What is needed is a gasket which can be installed without being loaded, then expanded and plastically deformed after the sealing surfaces are positioned and clamped together. An inflatable O-ring seal would have the necessary installation characteristics, but the service conditions sometimes (as in the Tokamak) preclude the use of elastomers.